Pipeline insulation means

ABSTRACT

An insulating section and a method for insulating a length of pipe in northern regions subseqeunt to installation of the pipe is provided by a prefabricated pipe insulation system comprising (a) forming a cylindrical metallic outer jacket longitudinally flanged for seaming, (b) applying a layer of synthetic insulating foam to the interior of the outer jacket thereby forming insulating sections of insulating material adhering to an outer jacket, (c) placing said sections end-to-end longitudinally and circumferentially along the length of pipe, (d) providing batten straps, adaptable to mating with the longitudinal seams, around the pipe circumference and extending between adjacent seams of insulating sections, and (e) securing the insulating section against the pipe and the circumferential battens by forming the longitudinal seam which incorporates the battens. The pipe insulating system provides a means of forming pipe insulation sections in a mobile unit near the pipe location and is particularly applicable in northern regions to insulate newly laid or existing pipelines.

United States Patent 91 Eliason [73] Assignee: Atlantic RichfieldCompany,

Philadelphia, Pa.

[22] Filed: July 30, 1973 [21] Appl. No.: 383,957

Related U.S. Application Data [62] Division of Ser. No. 196,630, Nov. 8,1971, Pat. No.

[52] U.S. Cl 138/149; 138/163 [51] Int. Cl. F161 9/14 [58] Field ofSearch 138/149, 151, 157, 163; 161/47, 104, 105, 106; 285/47, 424

[56] References Cited UNITED STATES PATENTS 347,631 8/1886 Merriam138/149 1,179,322 4/1916 Johnson 285/424 3,044,498 7/1962 Barnes et a1.161/104 3,068,026 12/1962 McKamey 285/47 3,307,590 3/1967 Carlson138/149 3,429,956 2/1969 Porter 138/149 3,559,694 2/1971 Volberg 138/1493,654,966 4/1972 Waksman 138/141 FOREIGN PATENTS OR APPLICATIONS 722,63211/1965 Canada 138/149 June 3, 1975 Primary Examiner-Herbert GoldsteinAttorney, Agent, or Firm-Coleman R. Reap [57] ABSTRACT An insulatingsection and a method for insulating a length of pipe in northern regionssubseqeunt to installation of the pipe is provided by a prefabricatedpipe insulation system comprising (a) forming a cylindrical metallicouter jacket longitudinally flanged for seaming, (b) applying a layer ofsynthetic insulating foam to the interior of the outer jacket therebyforming insulating sections of insulating material adhering to an outerjacket, (0) placing said sections end-to-end longitudinally andcircumferentially along the length of pipe, (d) providing batten straps,adaptable to mating with the longitudinal seams, around the pipecircumference and extending between adjacent seams of insulatingsections, and (e) securing the insulating section against the pipe andthe circumferential battens by forming the longitudinal seam whichincorporates the battens. The pipe insulating system provides a means offorming pipe insulation sections in a mobile unit near the pipe locationand is particularly applicable in northern regions to insulate newlylaid or existing pipelines.

7 Claims, 11 Drawing Figures PATBHEU Mi: 3 1975 SHEET PIPELINEINSULATION MEANS This is a divisional of application Ser. No. 196,630filed Nov. 8, 1971, now US Pat. 3,774,281.

BACKGROUND OF THE INVENTION Economic activity in northern regions,particularly in the Arctic environment has been stimulated by discoveryof underground natural resources such as oil and gas reserves. Recoveryof these resources and their transportation to a suitable site forfurther processing or transporting may require installation of variouspipelines. Although pipelines in more temperate zones are generallyplaced underground, pipeline construction in northern regions wherein apermafrost condition typically prevails may require in part constructionof an aboveground pipeline on high moisture content permafrost areas sothat the pipeline is substantially free from adverse environmentaleffects and other dangers such as subsidence and erosion caused bythawing of frozen substrata. Thus construction of an above groundpipeline in an Arctic environment requires development and applicationof additional technology in the field of pipeline insulation.

In northern regions pipeline insulation for an above ground pipelinemust be capable of withstanding a wide range of temperatures that willvary from up to +180F. within the pipe to 70F. or lower ambient airtemperatures. The design of the entire pipeline insulating system mustachieve substantial flexibility to compensate for the temperaturedifferentials between the internal heat of the fluid carried by thepipeline and the ambient conditions.

The pipeline insulation requires protection from damage by impact bothduring and after installation that may be caused by construction,indigenous animal life and accidental or malicious blows by persons and-/or equipment that could injure insulation without significant impactresistance. If the pipeline is above ground, the insulation system mustbe capable of withstanding the deleterious effect of ultraviolet lightand other potentially damaging rays transmitted by the atmosphere. Anacceptable pipeline for the Arctic environment must be capable ofeconomical installation in a sub-freezing environment and provide asystem minimizing transportation costs for components of the pipelineinsulation system. Furthermore, the insulation system should be capableof visual quality control to ensure substantially uniform distributionof the insulating material in such a manner that undesirable voids inthe insulation are easily detected. In addition, it is desirable thatany breakage in a pipeline be easily capable of detection by electronicor visual means.

Various methods of insulating pipelines are known and include suchmethods as wrapping the pipeline with an asbestos-type material,applying a layer of insulating material such as a foam, or forming amold around a pipe circumference to create an annular space that isfilled with an expandable insulating foam. The latter method creates theproblem of establishing proper quality control in that it is extremelydifficult to determine whether the annular space is filled withinsulating foam and satisfactorily void-free. Merely placing aninsulating layer around a pipeline may expose the insulating layer todegradation by ultraviolet rays and provides an insulation having onlyminor impact resistance. Similarly, a pipeline wrapped withasbestos-like material is susceptible to deterioration.

Therefore, a pipeline insulating system that is economic and practicalto install in low temperature environments, that resists deteriorationcaused by exposure to the atmosphere, and that provides impactresistance is desirable for an above ground pipeline in northernregions.

SUMMARY OF THE INVENTION It is an object of this invention to provideprefabricated insulating sections for a length of pipe, particularly innorthern regions such as the Arctic and sub- Arctic. It is a furtherobject of this invention to provide an insulating section capable ofbeing produced at an on-site location near the pipeline to be insulated.Still another object of this invention is to provide an economic andsimplified method of insulating a pipeline in northern regions. Anotherobject of this invention is to provide a pipeline insulation system thatwill be generally'resistant to damage by impact and resistant to thedegradative effect of ultraviolet light as well as being able to survivethe deleterious effects of a low temperature environment. A stillfurther object of this invention is to provide a means of insulating anaboveground pipeline. Still another object of this invention is toprovide a method of insulating a length of pipe wherein the insulationis easily susceptible to quality control.

These and other objects of the invention are accomplished by providing acylindrical prefabricated insulation section for insulating a length ofpipe wherein each insulating section has a cylindrical outer jackethaving an arc of or less and longitudinally flanged for seaming with alayer of insulating foam adhering to the interior surface of the outerjacket. The method for insulating the length of pipe comprises formingthe prefabricated insulating section having a cylindrical metallic outerjacket longitudinally flanged for seaming and a layer of syntheticinsulating foam adhering to the interior surface of the outer jacket,thereafter placing the insulating sections in an end-to-end arrangementlongitudinally and circumferentially along the length of pipe to beinsulated, applying coupling means for the sections around the pipecircumference and extending between adjacent circumferential seams ofthe insulating sections, and finally securing the insulating sectionsagainst the pipe by longitudinal seaming of the paired flanges whereinthe circumferential coupling battens are incorporated within thelongitudinal flange seams at the intersections.

DESCRIPTION OF THE INVENTION The advantages of the invention will becomemore apparent from the following description considered in conjunctionwith the accompanying drawings wherein:

FIG. 1 is a diagrammatic view of an assembly line system for formingprefabricated insulating sections;

FIG. 2 is a fragmentary sectional view taken along line A-A of FIG. 1illustrating the molds for forming the insulating sections;

FIG. 3 is a fragmentary perspective view of an installed prefabricatedinsulation system having compatible coupling means for circumferentialand longitudinal joining;

FIGS. 4 and 4a are perspective views of prefabricated insulating sectionquadrants;

FIGS. 5a, 5b, 5c, 5d, and 5e are perspective views showing sequentialsteps in longitudinal seaming; and

FIG. 6 is a perspective view illustrating a fragment of the insulatedpipeline.

Referring now in greater detail to the various views of the drawings,FIG. 1 illustrates an assembly line for forming the prefabricatedinsulating sections having sheet metal supply roll 2 representing asupply of metallic outer jacket material that is fed to straighteningrolls 4 and delivered to forming rolls 6 that set the cur vature ofouter jacket 8 to a cylindrically shaped contour and provide flangesalong both longitudinal edges, Outer jacket support conveyor 10 movesthe outer jacket to a position beneath foam mixing spray head(s) 11wherein synthetic foam layer 16, such as a polyurethane, is applied tothe interior surface of the outer jacket so that the foam covers theentire curved surface that will embrace the pipe to be insulated. Asfoam layer 16 rises, caused by foam formation, outer jacket supportconveyor 10 moves under upper form conveyor 18 wherein sheet supply roll12 feeds a sheet that serves as a mold release material between risingpolyurethane foam layer 16 and upper form conveyor 18. Thereafter, thecontinuous length of insulating section 20 moves to a cut off areawherein lengths of prefabricated insulating section are cut at desiredintervals.

Depending upon the nature and desired physical properties of the outermetallic jacket, any sheet metal material may be employed; preferredmaterials include aluminum, galvanized carbon steel, prepainted carbonsteel, galvanized and prepainted carbon steel, and stainless steel.

Although the preferred synthetic foam material is a polyurethanesuitable for use in a low temperature environment, other synthetic resinmaterials useful in low temperature environments may also be employed.

Sheet material 14 provides a mold release means between the upper dieand the foamed insulating material. In addition, the sheet provides aprotective shield for the foam layer of the insulating section that isuseful during any required transit to the installation'site andsubsequent handling from the time the insulating section is formed untilinstallation. As sheet material, various thermoplastic syntheticpolymeric materials may be employed including polyolefin sheets such aspolyethylene and polypropylene as well as vinyl chloride sheets.Alternatively, conventional mold release agents may be applied to theupper die in lieu of the synthetic polymeric sheet.

The pipe insulating system of this invention comprises a plurality ofinsulating sections installed circumferentially to the pipe, andlongitudinally as desired, wherein the individual insulating sectionsare cylindrical in shape having an arc of 180 or less. Thus eachinsulating section may be semi-cylindrical, having an arc of 180, sothat two sections surround the pipe or three or four insulating sectionsmay circumferentially cover the pipeline, thus each section would havean arc of 120 or 90, respectively. The desired circumferential arc ofthe insulating section will usually depend upon the size of the pipelineto be insulated. For instance, a pipeline of 48 inches in diameter maybe insulated by insulating section quadrants wherein each section formsan arc of 90. A 36 inch pipeline may be insulated using three 120sections as shown in FIG. 6, for example and an 18 inch or smallerpipeline may be insulated with semi-cylindrical sections.

The particular longitudinal length of the insulating section likewisemay be selected as desired by those prefabricating and/or installing thepipeline. Usually, the factors determining longitudinal length will beease of handling and available manpower to install the pipelineinsulation. As an example, the longitudinal length of the insulatingsections may vary from about 4 feet to 30 feet or more in length, butgenerally would be from about 6 feet to 20 feet or more for ease ofhandling.

Spray head 11 emits the foam components for providing the insulatinglayer. For purposes of illustration, only one spray head appears in FIG.1, but a plurality of spray heads may be desirable for the largerinsulating sections. If a polyurethane foam is desired, the polyol,catalyst and polyisocyanate components together with any necessaryblowing agent and other optional additives will be fed through linesinto mixing head 11, as is conventional in the art, wherein thecomponents will be mixed and dispensed through the spray head.

The thickness of the insulating layer is dependent upon environmentalconditions as well as the desired physical characteristics to beimparted to the insulated pipeline. For instance, in a 48 inch diameterpipeline, the thickness of the insulating layer may be as much as 4inches or more but can vary depending upon the aforementioned factors.

FIG. 2 is a fragmentary sectional view of the insulating sectionassembly line taken along line A-A of FIG. 1 illustrating formation ofan insulating section quadrant having outer jacket 8 adhering to foaminsulation layer 16 wherein sheet 14, preferably of polyethylene,provides mold release means between foam insulation layer 16 and upperdie 32 that may be of cast polyurethane. Since outer jacket 8 ismetallic, mold release means between lower die 30 and the outer jacketare generally unnecessary. Upper die 32 is provided with upper drivechain diagrammatically indicated at 34 to move the die and pressure bars38a, 38b, and 380 provide the requisite mold forming means to shape theinsulation section. Lower die 30 is moved by lower drive chaindiagrammatically indicated at 36. The dies may be formed from castpolyurethane to provide a relatively inexpensive die, since the shapewill be periodically altered depending upon the diameter and contour ofthe pipeline to be insulated, however, other conventionally usedmaterials may be employed.

The assembly line for forming the pipe insulating sections illustratedin FIG. 1 may be adjusted to operate at any normal linear speed butgenerally a speed in the range of about 5 to 10 linear feet per minutewill be satisfactory.

After inspection of the prefabricated pipe insulating sections to insurethat the foam insulation is essentially uniformly distributed and isotherwise satisfactory, the sections are transported to the pipelinesite for installation where they are placed end-to-end longitudinallyand circumferentially along the length of pipe desired to be insulated.

FIG. 3 illustrates a view of the circumferential coupling mated with thehorizontal standing seam. Batten straps for circumferential joining willgenerally be of thin gauge metal and may be attached to the outer jacketflange by clips or other suitable means. It is desirable to avoidexposing raw edges of metal to the environment since direct exposure tothe atmosphere promotes deterioration of the metal; therefore, the edgesof the batten strap that would be exposed circumferentially surroundingthe insulating sections may be folded back Exposure of metal edges alongthe longitudinal length of the insulated pipeline is avoided by themethod of forming the longitudinal seam which is preferably a doublestanding rib seam. If desired, a sponge gasket may be placed between thebatten strap and outer jacket. The batten strap is adaptable to matingwith the longitudinal seam to form an integral joint as illustrated inFIG. 3 showing a fragmentary view of the insulated pipe wherein foaminsulation 16 is sandwiched between pipe 39 and outer jacket 8. Battenstrap 37 mates with longitudinal double fold standing seam 35 to form anintegral joining means.

FIG. 4 illustrates a perspective view of an insulating section quadrantfor insulating a pipeline 48 inches in diameter comprising foaminsulation layer 16 adhering to outer jacket 8 for form a cylindricallaminate quadrant section having flange 40 sufficiently wide to provideadequate metal to form the double fold standing seam, wherein the flangegenerally extends about 1 to 3 inches and preferably about 1V2 inchesfrom the base of outer jacket 8 and being substantially perpendicular tothe surface of the outer jacket.

FIG. 4a is a perspective view of another embodiment of a prefabricatedinsulating section quadrant having outer jacket 8, longitudinal flanges40 and insulating layer 16 wherein independently spaced longitudinalribs 41a, 41b, and 41c extend the length of the prefabri: catedinsulating section and are generally parallel to each other and thelongitudinal edges of the section. A ribbed outer metallic jacketprovides additional strength for the installed insulation sections andthe ribs are formed by conventional means. Spaced crush strips 43a, 43b,and 43c positioned on insulating layer 16 extend longitudinally thelength of the section at spaced intervals and are generally parallel toeach other and the longitudinal edges. The optional crush strips may beformed in a mold of the type shown in FIG. 2 by designing the mold toprovide for formation of the strips during the foaming step. Since theinsulating section is principally intended for insulating pipelines inArctic and sub-Arctic regions wherein the pipelines may possess certainstructural or design irregularities, crush strips that may outwardlyprotrude from 1/16 inch to /2 inch, depending upon the size of the pipeto be insulated, compensate for these irregularities by physicallydeforming during longitudinally and circumferentially securing andtherefore aid in obtaining a secure fitting of the insulating sectionagainst the pipeline.

FIGS. 5a, 5b, 5c, 5d and 5e illustrate formation of the longitudinaldouble fold standing rib seam at sequential steps wherein the seam isformed by a seaming tool having a plurality of rolls wherein the rollsrotate the abutting flanges. In a nine roll seamer wherein the firstroll is a power drive roll, each of the remaining eight rolls rotate theflanges in increments of 45 to provide a double fold standing seam. Thesecond roll (first rotating roll) turns the upper half of the abuttingflanges 45, the third roll rotates the flanges an additional 45 so thatthe upper half of the flanges are essentially par allel to the outerjacket having been turned 90 and rolls four to nine continue thisprocess to completion of the second fold. Rolls four and five completethe first fold and rolls six to nine form the second fold. Rolls six tonine function in a similar manner to rolls two to five in that each ofthe rolls turn the flanges an additional 45. After completion of thedouble fold standing rib seam, no metal edges are exposed to theatmosphere and thus the seam is corrosion resistant.

FIG. 5a illustrates longitudinally abutting insulating sections havingouter jackets 8a and 8b and longitudinal flanges 40a and 40bperpendicular to the outer jacket surface. FIG. 5b illustrates theposition of the flanges after the upper portions are rolled FIG. 50indicates the position of the flanges after roll six, the beginning offorming the second fold. FIG. 5d illustrates the flange position afterroll eight wherein the second fold is continuing to be formed. FIG. 52illustrates the final position of the completed second fold whereindouble standing rib seam 35 secures the circumferential battens againstthe pipe insulating sections and additionally obviates any directexposure of raw metal edges.

In one embodiment of the invention a pipeline 48 inches in diameter isinsulated by the pipe insulation system of this invention by placingprefabricated insulating section quadrants circumferentially to the pipeexterior wherein each quadrant is approximately 15 feet in length. Theprefabricated insulation sections are formed in an assembly line whereina supply of thin gauge galvanized carbon steel, unwound from an outerjacket supply roll, passes between straightening rolls and throughquadrant forming rolls wherein the interior of the outer jacket isexposed to a polyurethane foam spray head ejecting an amount ofpolyurethane foam to provide an insulation thickness of about fourinches. If desired, the metal outer jacket may be ribbed or headed toprovide additional strength for the installed insulated sections. Theparticular rigid polyurethane foam is designed for low temperatureapplications and is prepared from polyol and polyisocyanate componentsusing trichlorofluoromethane, in an amount of about 2 percent by volume,as the blowing agent.

The polyurethane foam has these physical properties: Athermoconductivity of 0.13 BTU/Hr./Ft. /F./In. (k factor at 77F. asdetermined by ASTM-D-2326-64T using the probe method), a compressivestrength of 23 psi (5% deflection as determined by ASTM-D-l6- 21-64), awater absorption of 35 gms/l ,000 cm (as determined by ASTM-D-l2l7-62T)and an overall density of 2.7 lbs./ft. (as determined by ASTM-D-l6-22-63). Mold release means between the urethane foam and the upper dieis provided by polyethylene film that also serves to protect the foamsurface from minor abrasions or other damage that may occur between thetime of foam formation and time of installing the individual sections.The assembly line for the insulating sections then moves thecontinuously formed pipe insulation to a cut-off area. The insulatingquadrants are then installed end-to-end, circumferentially andlongitudinally, and joined by aforementioned means. During installationof the sections temporary holding straps will be used while thecircumferential battens are installed.

Although the sections may be placed against the pipe to be insulated sothat the longitudinal lengths are coextensive thus forming a continuouscircumferential seam around the pipe, it is generally preferable toemploy a staggered circumferential joint design thus forming adiscontinuous circumferential seam that provides additional strength forthe installed insulation sections. Large diameter pipeline insulation bythe aforementioned insulating sections may be economically installedeven in low temperature environments. Since the sections are relativelyeasy to install, installation may be accomplished even in sub-freezingtemperatures by providing temporary cover for the work area to protectthe installers from environmental conditions. The metallic outer jacketis resistant to deterioration caused by exposure to the atmosphere andprovides an impact resistant outer covering that is resistant todegradation by ultraviolet rays.

FIG. 6 illustrates a fragment of an insulated pipeline constructed inaccordance with the invention, comprising a pipeline 39; surroundinginsulation 16, and an outer metal skin 8 formed of three 120 sections;standing ribs 35; and a batten strap 37 all as fully described in theforegoing description.

While the preferred embodiments of the invention have been illustratedand described, it is to be understood that modifications may be madewithin the scope of the appended claims without departing from thespirit of the invention.

We claim:

1. An insulated pipeline having a plurality of insulation sectionssecured against the pipe by longitudinal and circumferential securingmeans at insulating section joints wherein said longitudinal securingmeans is a double fold standing rib seam formed by doubly folding pairsof flanges extending radially outward from the longitudinal edges ofcircumferentially adjacent insulation sections and said circumferentialsecuring means comprises batten straps free of exposed edges.

2. An insulated pipeline according to claim 1 wherein said insulatingsections comprise an outer metallic jacket and a layer of insulatingfoam adhering to the interior surface of the outer jacket.

3. An insulated pipeline according to claim 2 wherein the transverseedge of said insulation sections forms an arc of about to 4. Aninsulated pipeline according to claim 2 wherein said jacket is made froma metal selected from aluminum, carbon steel, and stainless steel.

5. An insulated pipeline according to claim 2 wherein said insulatingfoam is polyurethane.

6. An insulated pipeline according to claim 1 wherein the edges of saidbatten straps are folded back 180.

7. An insulated pipeline according to claim 6 wherein the ends of saidbatten straps are incorporated in the double fold standing rib seam.

1. An insulated pipeline having a plurality of insulation sectionssecured against the pipe by longitudinal and circumferential securingmeans at insulating section joints wherein said longitudinal securingmeans is a double fold standing rib seam formed by doubly folding pairsof flanges extending radially outward from the longitudinal edges ofcircumferentially adjacent insulation sections and said circumferentialsecuring means comprises batten straps free of exposed edges.
 1. Aninsulated pipeline having a plurality of insulation sections securedagainst the pipe by longitudinal and circumferential securing means atinsulating section joints wherein said longitudinal securing means is adouble fold standing rib seam formed by doubly folding pairs of flangesextending radially outward from the longitudinal edges ofcircumferentially adjacent insulation sections and said circumferentialsecuring means comprises batten straps free of exposed edges.
 2. Aninsulated pipeline according to claim 1 wherein said insulating sectionscomprise an outer metallic jacket and a layer of insulating foamadhering to the interior surface of the outer jacket.
 3. An insulatedpipeline according to claim 2 wherein the transverse edge of saidinsulation sections forms an arc of about 90* to 180*.
 4. An insulatedpipeline according to claim 2 wherein said jacket is made from a metalselected from aluminum, carbon steel, and stainless steel.
 5. Aninsulated pipeline according to claim 2 wherein said insulating foam ispolyurethane.
 6. An insulated pipeline according to claim 1 wherein theedges of said batten straps are folded back 180*.